fix bug of undo/redo creating new change operations themselves

test/src/test_Buffer.cc

@@ -195,6 +195,10 @@ TEST(BufferTest, allows_undo_and_redo_of_inserts)
     b.redo();
     EXPECT_EQ(ss("12abc\nd3ef$\nghi\n"), b.get_string());
     EXPECT_EQ(C('d'), **it);
+
+    /* undo/redo do not create new operations */
+    EXPECT_FALSE(b.m_current_change_operation);
+    EXPECT_EQ(3u, b.m_change_operations.size());
 }
 
 TEST(BufferTest, allows_undo_and_redo_of_erases)
@@ -247,6 +251,10 @@ TEST(BufferTest, allows_undo_and_redo_of_erases)
     b.redo();
     EXPECT_EQ(ss("bc\ndfghi\n"), b.get_string());
     EXPECT_EQ(C('f'), **it);
+
+    /* undo/redo do not create new operations */
+    EXPECT_FALSE(b.m_current_change_operation);
+    EXPECT_EQ(3u, b.m_change_operations.size());
 }
 
 TEST(BufferTest, erase_chunks_are_coalesced_within_a_change_operation)